The present invention relates to an escalator which may be used not only by a general healthy pedestrian but also a person who must use a wheel chair. More particularly, the invention is concerned with an escalator staircase structure which is safe in moving a wheel chair up and down.
An escalator has been widely used as a serviceable equipment for general healthy pedestrians or walkers. Recently, various escalators have been used also in various public facilities such as a city traffic system. Accordingly, there is a strong demand such that the escalators be serviceable not only for general pedestrian but also physically handicapped people who must use wheel chairs.
However, the thus far proposed general escalators have been made only in consideration of the general healthy pedestrians as described above. For this reason, a fore and back length or a longitudinal length of tread boards of the escalator is kept at about 400 mm. This dimension is sufficient for the healthy pedestrians but, in the case where the people using their wheel chairs rides on the escalator, that dimension is too small in comparison with a size of the wheel chair so that there is a great fear that they would fall down with great danger. Therefore, it is generally understood that it is impossible to make the escalators serviceable for the wheel chair users.
Nevertheless, in view of recent stronger public opinion and spread of behavior area of the wheel chair users, a serviceable application of the escalators to the wheel chair users becomes a serious task to be solved. Thus, various attempts have been made to deal with this problem.
For example, Japanese Patent Publication No. 41555/81 discloses an escalator in which a special tread board having a larger fore and back dimension is provided among staircase steps of the escalator. Also, Japanese Patent Laid-open No. 12067/84 discloses an escalator which has a mechanism for widening, as desired, the fore and back dimension of the tread board among the staircase steps. Also, Japanese Patent Laid-open No. 203085/84 discloses a mechanism for elevating a specific tread board using an electric power as desired, so that the specific board may be kept at the same level as that of a tread board of the adjacent fore or rear staircase step, thereby widening the effective area of the tread surface. However, any of the escalators according to these techniques must involve a complicated structure. Furthermore, the escalators according to these techniques are serviceable to some extent but is not satisfactory in safety aspect.